You will never notice 25 lbs taken off the front end of your otherwise stock car. Similar the performance gains from the aftermarket design. If you were making other changes, (cam, compression ratio) my advice might differ. That said, there is no reason to avoid the aluminum dual-plane design other than cost benefit ratio.
Of much greater concern will be adapting your throttle cables and kickdown linkage if you can't score those parts from a junkyard.
Sometime in the next few weeks I'll be swapping out the 2bbl intake on my stock 400 to an OEM iron intake/used Edlebrock. The primary driver for that is just the superiority of the Edlebrock carb vs. the OEM 2bbl, not because I plan to drag race anyone with my otherwise bone-stock '76 Royal Monaco. I also plan tosimply modify/fab my linkage rather than chase down the parts. I can make a point to detail this process for you with photos if you've never done such a thing.
Someone mentioned emissions... I don't know if that's a concern in your state. The car won't get "dirtier" (in fact, it will probably clean-up) but some boneheaded states which require all original parts vs. a simple tailpipe test.
Regarding driveability... I've put T-body EFI systems on two engines. My feeling is "meh". They have their own trade offs and again, the cost benefit ratio is again poor vs. a well tuned and functional Edlebrock. In about 30 mins, I'm going to drive this old carb'ed monster 35 miles one-way to work, as I've been doing for weeks while my "modern" car is sidelined waiting for me to install front brakes.
